Hurricane DEAN (Text)

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HURRICANE DEAN DISCUSSION NUMBER 15
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL042007
1100 PM EDT THU AUG 16 2007
THE SATELLITE PRESENTATION OF DEAN HAS DETERIORATED A BIT OVER THE
LAST 12 HOURS...WITH NO EVIDENCE OF AN EYE IN CONVENTIONAL OR
MICROWAVE IMAGERY. THE SFMR INSTRUMENT ON THE EARLIER AIR FORCE
FLIGHT RECORDED A PEAK SURFACE WIND OF 88 KT AROUND 19Z IN THE
SOUTHEAST PORTION OF THE EYEWALL...ALONG WITH VERY LITTLE WIND IN
THE SOUTHWEST QUADRANT OF THE CIRCULATION. BASED ON THE EARLIER
AIRCRAFT DATA AND RECENT STRUCTURAL TRENDS...THE INITIAL INTENSITY
IS HELD AT 85 KT. COMMUNICATIONS DIFFICULTIES DURING THE
RECONNAISSANCE MISSION PREVENTED MUCH OF THE DATA FROM GETTING TO
US...BUT DROPSONDE DATA CALLED IN AFTERWARD BY THE CREW INDICATE
THE CENTRAL PRESSURE IS A LITTLE LOWER THAN PREVIOUSLY ESTIMATED...
ABOUT 976 MB.
THE INITIAL MOTION IS 275/22. DEAN IS SOUTH OF A MID-LEVEL RIDGE
THAT HAS BEEN MOVING WESTWARD IN TANDEM WITH THE CYCLONE. GLOBAL
MODEL GUIDANCE IS IN EXCELLENT AGREEMENT THAT IT WILL CONTINUE TO
DO SO FOR MOST OF THE FORECAST PERIOD...AND THE GUIDANCE IS VERY
TIGHTLY CLUSTERED ON A WEST TO WEST-NORTHWEST TRACK FOR AT LEAST
THE NEXT 72 HOURS. AFTER THAT...THE TRACK OF DEAN WILL DEPEND ON
HOW MUCH INTERACTION THERE IS BETWEEN THE HURRICANE AND A MID- TO
UPPER-LEVEL LOW CURRENTLY NORTHEAST OF THE BAHAMAS. ALL THE
AVAILABLE GUIDANCE CURRENTLY MOVES THIS LOW WESTWARD OUT OF THE WAY
AND SHOWS VERY LITTLE INTERACTION BETWEEN THE TWO...AND HENCE ONLY
A MODEST RIGHTWARD BEND IN THE TRACK ON DAYS 4 AND 5. THE
OFFICIAL FORECAST IS BASICALLY AN UPDATE OF THE PREVIOUS ADVISORY
TRACK. GIVEN THE UNCERTAINTY IN GLOBAL MODEL FORECASTS AT LONG
RANGES HOWEVER...A DIFFERENT EVOLUTION WITH THE UPPER LOW IS NOT
OUT OF THE QUESTION.
DEAN CONTINUES TO EXHIBIT A STRONG OUTFLOW PATTERN...AND THIS
FAVORABLE UPPER FLOW IS EXPECTED TO PERSIST FOR THE NEXT TWO TO
THREE DAYS. DATA FROM THE NOAA G-IV MISSION THIS EVENING SHOW NO
EVIDENCE OF UNFAVORABLE THERMODYNAMICS IN THE NEAR ENVIRONMENT...
AND THE AVAILABLE OBJECTIVE GUIDANCE INDICATES CONTINUED
STRENGTHENING IN THE CARIBBEAN. THE UPPER FLOW COULD BE A LITTLE
LESS FAVORABLE IN THE WESTERN CARIBBEAN...PARTICULARLY IF THE UPPER
LOW LAGS A BIT. THE OFFICIAL FORECAST CALLS FOR SLIGHTLY FASTER
DEVELOPMENT THAN THE PREVIOUS ADVISORY BUT ENDS UP IN THE SAME
PLACE...AND IS IN GOOD AGREEMENT WITH THE AVAILABLE OBJECTIVE
GUIDANCE.
FORECAST POSITIONS AND MAX WINDS
INITIAL 17/0300Z 14.1N 58.7W 85 KT
12HR VT 17/1200Z 14.5N 61.9W 90 KT
24HR VT 18/0000Z 15.1N 65.8W 95 KT
36HR VT 18/1200Z 15.7N 69.2W 105 KT
48HR VT 19/0000Z 16.4N 72.6W 115 KT
72HR VT 20/0000Z 18.0N 80.0W 120 KT
96HR VT 21/0000Z 19.5N 86.0W 120 KT
120HR VT 22/0000Z 22.0N 92.0W 90 KT
$$
FORECASTER FRANKLIN
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